No, income reinvested in the unit trusts will be used to purchase additional units, which will have their own base cost. As an example, assume that you hold 100 000 units with a total base cost of R50 000 and interest of R5 000 is reinvested to purchase an additional 800 units. The total base cost will increase to R55 000 and, if the 10 800 units are sold for R75 000, the capital gain will be R20 000, not R25 000.